1. Field of the Invention
The present invention relates in general to an ink jet type recording head having a case in which (1) a flow path unit forming pressure generating chambers communicating with nozzle openings, (2) a pressure means for pressurizing the pressure generating chambers and (3) a semiconductor integrated circuit for supplying a drive signal to the pressure means are installed, and more particularly to a protective technology for the semiconductor integrated circuit.
2. Description of Related Art
When a length vibration mode of a piezoelectric vibrator, which is described in Patent Laid Open Hei. 5-104715, is used for driving an ink jet type recording head, a contact area where the piezoelectric vibrator contacts a diaphragm is made extremely small, which performs a resolution such as more than 180 dots per inch in each unit.
The length mode of a piezoelectric vibrator is bonded to a fixed base at a predetermined interval and installed in a vibrator unit, and a drive signal/signals is/are independently supplied to each vibrator via a flexible cable from an external drive circuit.
However, in the case of a recording head for a high density printing, in which a pressurizing means such as a piezoelectric vibrator is fixed from 70 xcexcm to 150 xcexcm (180-360 dpi), the width of the conductive pattern is inevitably narrow such as from 20 xcexcm to 50 xcexcm. Therefore, electrical resistance is increased substantially when many conductive patterns are formed in a limited width of the flexible cable.
In order to solve such problems, a flexible cable A shown in FIG. 24 is divided into area B for transferring the drive signal to an piezoelectric vibrator and area C for transferring a print signal from an external drive circuit to the integrated semiconductor. A window D is formed at boundaries therebetween where a semiconductor integrated circuit E is supplied to convert the print signal into the drive signal, which drives each pressurizing means. The print signal is transmitted to the semiconductor integrated circuit E from the external drive circuit through conductive patterns F, whose number is less than that of the pressurizing means. The drive signal is supplied to each pressurizing means through conductive patterns G, whose number is the same as that of the pressurizing means. Therefore, the number of the conductive patterns F is fewer than the number of conductive patterns G, and the conductive patterns F have a relatively long length. As a result, electric resistance is decreased by expanding the conductive patterns F. The numeral H designates a ground connection.
However, when drive frequency is increased because of a high-speed printing, temperature of the semiconductor integrated circuit is increased, which makes the circuit uncontrolled.
The present invention relates to an ink jet type recording head having a case, in which (1) a flow path unit forming pressure generating chambers communicating with nozzle openings, (2) a pressure means for pressurizing the pressure generating chambers, and (3) a semiconductor integrated circuit for supplying a drive signal to the pressure means are installed, and heat caused by high frequency drive signals in the semiconductor circuit is promptly dissipated to the outside from exposed parts thereof, which prevents the semiconductor integrated circuit from being uncontrolled by the heat.
Therefore, an object of the present invention is to provide an ink jet recording head, which prevents the semiconductor integrated circuit installed in the recording head with the pressurizing means from being uncontrolled.